The proposed study is designed to investigate the chemical nature and biosynthesis of epidermal cell components (i.e., keratohyalin granules, nucleus) observed morphologically under normal, experimental and pathological conditions, in order to better understand biochemical changes involved in each stage of epidermal cell differentiation (the "keratinization" process). Factors influencing the process will be investigated and elucidation of control mechanisms is sought. Cytochemical, autoradiographical, chemical and immunological techniques will be used. These results will clarify pathomechanisms of skin diseases associated with abnormal keratinization and contribute to the control of these diseases.